For various reasons crops sometimes are lying so close to the ground that it is difficult to cut them with a conventional harvest header. Some crops are inherently short, while others may be taller, but are prone to fall down when they reach maturity. Heavy rain or hail can also cause crop to be lying close to the ground at harvest time.
Typically the knife on cutting headers comprises a knife bar extending along the front lower edge of the header, with a plurality of triangular knife sections attached to the bar such that the apex of the triangle extends forward from the bar. The exposed side edges of the knife sections are sharpened. Guards are attached to the front lower edge of the header and serve to protect the knife sections from breakage when contacting stones and like obstructions. The guards comprise pointed guard fingers extending forward, and the knife moves back and forth along the edge of the header in a slot cut laterally through the guard fingers. In addition to protecting the knife, the guard fingers also enable the knife sections to cut the crop. As the knife section moves back and forth it pushes crop against the sides of those portions of the guard finger that are above and below the slot, shearing the crop stalks.
A conventional knife is a few inches above the ground when the header is in its lowest position, such that very short or downed crop material will pass under the knife and be lost. Many different kinds of “crop lifters”, as they have come to be known, have been developed over the last century and more. Typically these crop lifters are attached to the header and/or the forward extending point of the guard finger, and provide an arm of various designs that rides along the ground ahead of the knife. A lifting finger extends at a shallow angle from the front of the arm back and over the knife. As the header moves down the field, the arm rides along the ground and under the downed crop stalks, which then are lifted and pass over the lifting finger to the knife, where they are cut and continue moving onto the header from where they can be passed to the harvester, swather table, or the like.
U.S. Pat. Nos. 700,029 and 791,022 to Gatermann, U.S. Pat. No. 2,734,332 to Fisher, U.S. Pat. No. 2,892,298 to Chaney, U.S. Pat. No. 2,960,814 to Babcock, and Canadian Patent Number 407,654 to Young disclose such a crop lifter that is pivotally attached to the header so as to be able to move up and down to follow the ground. The Babcock and Fisher devices float on the ground, while the others are biased toward the ground by springs. U.S. Pat. No. 4,120,138 to Schumacher illustrates a crop lifter that is fixed to the header instead of pivoting, but is made of spring steel so that same may move up and down to follow the ground.
Crop lifters interfere somewhat with normal operations of the header when harvesting taller crops with the header raised a substantial distance above the ground. During turns in particular, because the crop lifters generally extend a considerable distance ahead of the header, some crop stalks are pushed over and not cut. It is common practice therefore to remove the crop lifters when using the header on taller crops. In view of this there is also considerable prior art directed to providing a crop lifter that is easily installed and removed.
U.S. Pat. No. 3,579,967 to Schumacher discloses a quick attachment mechanism for a crop lifter. A rear end of a springy arm of the crop lifter defines a notch between legs that fit into an annular leg groove in a nut that attaches the guard to the header. The extreme rear end of the legs of the notched portion are bent down, such that the legs can only be inserted into the leg groove when the front end of the arm is tilted downward. After insertion, the front end of the arm is raised, and a hook is placed over the guard finger to lock the arm in tension and in the raised position. With the arm so raised, the bent portion at the rear of the arm prevents the arm from moving forward and disengaging the grooved nut.
U.S. Pat. Nos. 4,295,328 and 6,442,919 and United States Patent Application Publication 2003/0005678 of Schumacher disclose quick attachment mechanisms for crop lifters that use the bent rear notch and provide alternate mechanisms using springs, clips and the like to hold the arm in the raised position by releasably securing the arm to the guard finger.
Canadian Patent Numbers 548,220 to A. Claas and 719,825 to R. Claas disclose a quick attachment mechanism for a crop lifter that attaches only to the guard finger with a spring biased clamp.